Why do you doubt that? If you went back in time, and made the changes in the past that led to you having gone to med school, it would either create a new timeline, the version of you that went back in time wouldn’t exist, you would somehow destroy reality, or if there is some kind of persistent self across changes in time you would then have the knowledge. Even theoretically there’s no theory of time travel where you could go back in time, cause yourself to gain knowledge, go forward in time, and not have that knowledge.